|CCC|IEEE Conference on Computational Complexity|1993|1996|1999|-|2007|2011|2015|
|---|---|---|---|---|---|---|---|---|
|EC|ACM Conference on Electronic Commerce|-|-|-|2003|2007|2011|2015|
|ISCA|ACM/IEEE International Symposium on Computer Architecture|1993|1996|1999|2003|2007|2011|2015|
|LCTES|ACM SIGPLAN/SIGBED Conference on Languages, Compilers, and Tools for Embedded Systems|-|-|1999|2003|2007|-|-|
|METRICS|ACM SIGMETRICS International Conference on Measurement and Modeling of Computer Systems|-|1996|1999|2003|2007|-|2015|
|PLDI|ACM SIGPLAN Conference on Programming Language Design and Implementation|-|1996|1999|2003|2007|2011|2015|
|PODC|ACM Symposium on Principles of Distributed Computing|-|1996|1999|-|-|2011|-|
|PPoPP|ACM SIGPLAN Symposium on Principles and Practice of Parallel Programming|1993|-|1999|2003|-|-|-|
|SPAA|ACM Symposium on Parallelism in Algorithms and Architectures|-|-|-|2003|2007|2011|2015|
|SoCG|ACM Symposium on Computational Geometry|1993|1996|-|2003|-|-|-|
|STOC|ACM Symposium on Theory of Computing|1993|1996|1999|2003|2007|2011|2015|

Question: what is the next previous year prior to 2015 on the chart?
Answer: 2011